US2186177A - Art of coating metal surfaces with a water insoluble metallic phosphate - Google Patents

Art of coating metal surfaces with a water insoluble metallic phosphate Download PDF

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Publication number
US2186177A
US2186177A US292543A US29254339A US2186177A US 2186177 A US2186177 A US 2186177A US 292543 A US292543 A US 292543A US 29254339 A US29254339 A US 29254339A US 2186177 A US2186177 A US 2186177A
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United States
Prior art keywords
solution
coating
tank
cleaning
phosphate
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US292543A
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English (en)
Inventor
Gerald C Romig
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Henkel Corp
Original Assignee
Amchem Products Inc
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Publication date
Application filed by Amchem Products Inc filed Critical Amchem Products Inc
Priority to US292543A priority Critical patent/US2186177A/en
Application granted granted Critical
Publication of US2186177A publication Critical patent/US2186177A/en
Priority to DEA1486D priority patent/DE862848C/de
Priority to CH247997D priority patent/CH247997A/de
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/78—Pretreatment of the material to be coated

Definitions

  • This invention relates to the art of producing phosphate coatings on metal surfaces, and more specifically to the production of such coatings on ferrous metal surfaces, and the present application is a continuation in part of my earlier appli-. cation Serial No, 228,401, filed September 3, 1938.
  • alkali cleaning Probably the most convenient and economical method for removing grease, oil, solid dirt, etc., is the process loosely known in the art as alkali cleaning.
  • the surfaces to be cleaned are treated with solutions of alkaline chemicals such as caustic soda, soda ash, trisodium phosphate, borax, sodium silicate, etc.
  • alkaline chemicals such as caustic soda, soda ash, trisodium phosphate, borax, sodium silicate, etc.
  • These solutions may also contain emulsifying agents such as soap, solvents such as kerosene, etc., and they may be used hot or cold and the work may be immersed in the solution or may be sprayed therewith.
  • the alkaline cleaning process employs hot dilute solutions of a mixture of alkalies, with or without soap or other emulsifying agent.
  • solvents such as hydrocarbons, chlorinated hydrocarbons, etc.
  • solvent cleaning may involve dipping the work to be cleaned into a solvent, wiping it with a rag soaked in a solvent, or exposing the cold work to the vapor of a solvent, this latter being known as vapor degreasing. Combinations of these various solvent cleaning meth-' ods are also frequently employed.
  • the type of steel or iron being coated also has an influence on the finished coating as well as upon the rate at which the replenishing chemicals must be added to the coating solution.
  • the principal object of the present invention is to effect a marked saving in the consumption of chemical used in the coating process.
  • Further objects are the production of coatings of greater uniformity on a long succession of surfaces, reduction in the amount of suspended solids in the coating solution (usually referred to as sludge) greater ease of rinsing of the coated surfaces, less frequent cleaning of heating coils, etc., in the coating solution reservoir, besides other objects which will appear to those skilled in this art, in connection with the following description of the invention.
  • my invention resides in the discovery that the foregoing difliculties may be largely overcome and the objects of the invention consistently obtained if the hydrogen ion concentration of the rinse water usedto remove the residues of the cleaning operation just prior to the coating step is maintained between approximately pH 4.2 and pH 6.
  • the optimum range within these limits may vary somewhat depending upon the type of steel being processed. I do not know with what property of the steel the optimum pH of the rinse water is to be correlated, but many experiments and observations have shown that it will vary slightly depending upon the type of steel being processed.
  • the means by which the pH of the rinse water prior to the coating operation is kept within this range may be any known to the chemist, but as a practical matter, where alkali cleaning is employed, I find it distinctly advantageous to counteract the tendency of the alkali carried over from the cleaning operation to raise the pH of the rinsing water prior to the coating step, by feeding back some or all of the final rinse water which is employed after the coating operation.
  • This final rinse water obviously contains acid coating solution and by feeding back some or all of such rinse water to the rinsing step which follows the alkali cleaning operation it is generally possible to maintain the pH within the range specified without the addition of any other acid or acid salt.
  • supplemental acid or acid salt may be added in the form of acetic acid, sodium hydrogen sulphate, hydrochloric acid, etc., although I prefer to add phosphoric acid or admixtures of phosphoric acid with one of its salts, because this is the acid employed in the coating solution.
  • my invention is peculiarly adapted for use in connection with the so-called spray process of phosphatic coating, and furthermore, it is markedly advantageous in connection with a spray process which utilizes an aqueous acid phosphate coating solution other than ferrous phosphate, such, for example, as zinc phosphate or manganese phosphate.
  • an aqueous acid phosphate coating solution other than ferrous phosphate such as zinc phosphate or manganese phosphate.
  • the coating solution is maintained substantially free of dissolved iron by suitable additions of a salt of nitrous acid, such as sodium nitrite, in accordance with the disclosure contained in my prior Patent No. 2,132,883, issued October ll, 1938. Therefore, by way of specific example, I will describe my invention as it is applied in connection with a spray process of the character mentioned.
  • the following description involves the coating of a succession of stamped and welded refrigerator cabinets and doors.
  • the pieces were ground smooth on the welded joints and were then hung on a monorail conveyor of a conventional four tank processing machine, the apparatus being arranged so that the pieces or stampings to be coated passed successively through the four compartments of the machine.
  • the surface of the pieces was subjected to the action of jets of liquid, forced by a pump from a collecting tank beneath the stampings through appropriate pipes and spray nozzles, the excess liquid draining from the surfaces, returning to the tank from which it had been drawn.
  • the first tank of the washing machine contained a hot dilute solution comprising sodium metasilicate and caustic soda.
  • the second tank contained hot rinse water and was provided with means for repeatedly and continuously changing the water as required.
  • the third tank contained the coating solution, maintained at a temperature of 170 F.
  • the coating solution was zinc phosphate, which, during operation, was continuously replenished by adding thereto, through a flow meter, a solution of zinc phosphate.
  • To this tank also was substantially continuously added, through a flow meter, 2. water solution of sodium nitrite sufficient to maintain the solution substantially free of dissolved iron.
  • the fourth tank contained hot rinse water which could be continually changed by introducing a. stream of fresh water.
  • the coating solution for tank No. 3 was formed by diluting to about fifty times its original volume a concentrated solution constituted as follows:
  • Replenishment of the coating solution during the coating operation was made by continuously adding, as needed, to the coating solution in tank No. 3 regulated quantities of the concentrated zinc phosphate solution of Formula No. l. Hourly analyses were made to determine the rate of addition.
  • tank No. 2 In order to prevent the rinse water in tank No. 2 from becoming alkaline, overflow from tank No. 4 from the final rinse water after the coating operation was conducted back to tank No. 2, to take the place of the addition of fresh water to such tank.
  • the pH of tank No. 2 can nearly always be maintained within the specified range, i. e., pH 4.2 to pH 6, by so feeding back from tank No. 4 to tank No. 2, the neutralizing and buffering action of the feed-back rinse water being sufiicient for this purpose.
  • additional acid chemical may be supplied to tank No. 2 in order to maintain the desired pH therein. I have found, as stated above, that this can be done in various ways, although I prefer to use phosphoric acid or a small amount either of the solution of Formula No. 1 given above or of a little of the diluted coating solution used in tank No. 3.
  • the fiow of sodium nitrite solution required was generally but 3 to 3% gallons per hour and the same of zinc phosphate solution. But even with this arrangement, occasional unaccountable variations in the amounts of the reagents required by the coating tank were noted and careful observation showed that these variations were directly associated with fluctuations in the pH of the rinse water in tank No. 2.
  • the method which includes cleaning the surface with an alkaline cleaning solution, rinsing the surface after said cleaning operation with an aqueous solution having an acidity within the range pH 4.2 to pH 6, spraying a succession of pieces so cleaned and rinsed with an aqueous acid phosphate coating solution which is substantially free of dissolved iron, collecting the runoff for reuse in the spraying operation, and substantially continuously adding to the solution regulated quantities of the acid phosphate and of a soluble salt of nitrous acid sufficient to maintain the sprayed solution substantially constant as to its metal content and also substantially free of dissolved iron.
  • substantially continuously operable method which includes the following steps applied to a succession of pieces, 1. e., cleaning the surfaces with an alkaline cleaning solution; rinsing the surfaces with an aqueous solution having an acidity within the range pH 4.2 to pH 6; spraying the surfaces with a zinc phosphate solution; collecting the run-oft for reuse in the spraying operation; and substantially continuously adding to the soassent?

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Treatment Of Metals (AREA)
US292543A 1939-08-30 1939-08-30 Art of coating metal surfaces with a water insoluble metallic phosphate Expired - Lifetime US2186177A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US292543A US2186177A (en) 1939-08-30 1939-08-30 Art of coating metal surfaces with a water insoluble metallic phosphate
DEA1486D DE862848C (de) 1939-08-30 1940-02-19 Verfahren und Vorbehandlung von alkaligereinigten Metalloberflaechen vor dem Aufbringen von Phosphatueberzuegen
CH247997D CH247997A (de) 1939-08-30 1945-12-17 Verfahren zur Herstellung von Phosphatüberzügen auf Metallen.

Applications Claiming Priority (1)

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US292543A US2186177A (en) 1939-08-30 1939-08-30 Art of coating metal surfaces with a water insoluble metallic phosphate

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US2186177A true US2186177A (en) 1940-01-09

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CH (1) CH247997A (de)
DE (1) DE862848C (de)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2473614A (en) * 1945-12-13 1949-06-21 American Chem Paint Co Method of and material for protecting and conditioning metal surfaces
US2481977A (en) * 1945-05-19 1949-09-13 Cinamon Lionel Metal protective coating method
US2516685A (en) * 1944-04-19 1950-07-25 American Chem Paint Co Process of preparing iron and aluminum surfaces to receive organic coatings and solution therefor
US2634223A (en) * 1949-07-01 1953-04-07 Standard Oil Dev Co Method for inhibiting corrosion in storage vessels
DE969369C (de) * 1949-09-06 1958-05-22 Metallgesellschaft Ag Verfahren zur Herstellung von Phosphatueberzuegen auf Zink
US2839439A (en) * 1955-06-07 1958-06-17 Detrex Chem Ind Method and composition for producing phosphate coatings on metal
DE969976C (de) * 1947-11-22 1958-08-07 Metallgesellschaft Ag Verfahren zur Herstellung eines Phosphatueberzuges auf Eisenwerkstoffen
US3493440A (en) * 1964-09-03 1970-02-03 Hooker Chemical Corp Method for phosphate coating ferrous metal surfaces and finishing treatment thereof
US3501352A (en) * 1965-08-02 1970-03-17 Hooker Chemical Corp Composition and method for treating zinc surfaces

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2516685A (en) * 1944-04-19 1950-07-25 American Chem Paint Co Process of preparing iron and aluminum surfaces to receive organic coatings and solution therefor
US2481977A (en) * 1945-05-19 1949-09-13 Cinamon Lionel Metal protective coating method
US2473614A (en) * 1945-12-13 1949-06-21 American Chem Paint Co Method of and material for protecting and conditioning metal surfaces
DE969976C (de) * 1947-11-22 1958-08-07 Metallgesellschaft Ag Verfahren zur Herstellung eines Phosphatueberzuges auf Eisenwerkstoffen
US2634223A (en) * 1949-07-01 1953-04-07 Standard Oil Dev Co Method for inhibiting corrosion in storage vessels
DE969369C (de) * 1949-09-06 1958-05-22 Metallgesellschaft Ag Verfahren zur Herstellung von Phosphatueberzuegen auf Zink
US2839439A (en) * 1955-06-07 1958-06-17 Detrex Chem Ind Method and composition for producing phosphate coatings on metal
US3493440A (en) * 1964-09-03 1970-02-03 Hooker Chemical Corp Method for phosphate coating ferrous metal surfaces and finishing treatment thereof
US3501352A (en) * 1965-08-02 1970-03-17 Hooker Chemical Corp Composition and method for treating zinc surfaces

Also Published As

Publication number Publication date
CH247997A (de) 1947-04-15
DE862848C (de) 1953-01-12

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